If the pixels are wider than they are tall, then the JPEG metadata should
have xDensity (what OIIO reports as "XResolution", using the TIFF
terminology) SMALLER than the xDensity (OIIOs "YResolution").
There are no Density tags in the EXIF spec, but XResolution and YResolution
do exist.
The "working version" rendered from Nuke, as you reported, said that the
XResolution = 2400 and YResolution = 1200. That is supposed to mean
pixels that are taller than they are wide, because the density of pixels
is
higher horizontally than vertically.
Based on the language in the EXIF spec, I'm not sure this is true. As I
mentioned in my previous message, the spec says this about the Resolution
tags:
The number of pixels per <ResolutionUnit> in the <ImageWidth>
direction. [...]
And here is the complete tag definition for ResolutionUnit (taken from
http://www.exiv2.org/Exif2-2.PDF):
---------------------------
ResolutionUnit
The unit for measuring XResolution and YResolution. The same unit is used
for both XResolution and YResolution.
If the image resolution in unknown, 2 (inches) is designated.
Tag = 296 (128.H)
Type = SHORT
Count = 1
Default = 2
2 = inches
3 = centimeters
Other = reserved
---------------------------
Using this language as a guide, an XResolution of 2400 and a YResolution of
1200 makes sense for an image with a pixel aspect of 2.0, and I believe this
is how other applications (Adobe, RV, Nuke) handle "non-square pixels" in
JPEG files.
-Nathan
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